what gears should I run in my 3/4 ton lifted gmc?

[ruedger455]

Ok guys I just had the engine in my 77 lifted gmc rebuilt. Its a chevy 350 with about 375 hp. Im running 35" tires on a 6 inch lift. Front axle is a d44 and the rear is a corp 14 bolt ff. Im pretty sure that my rear gear is 3.73, but not sure. All I know is that the truck has a hard time getting the tires rolling so I was thinking I need to swap gears. Im thinking that 4.56 in the front and rear will be good. I plan on getting 37" tires eventually and the 4.56s sound like they will move that rubber pretty good. My truck now wont even spin the tires in gravel!!! Would putting 4.56 gears give me burnout potential? Let me know what you guys suggest. My ring gear is 10.5 I think. Whats the best company to get these from as well?

Thanks guys, kimber

 

[350runner]

Not to be rude dude but 375hp would roast any tire...but ya the higher the better...

 

[ruedger455]

The guy that built it said on the dyno that it peaked at 374 at the flywheel. He could have just been trying to make his build seem better, very possible. But when I get on it while on the street it gets up and goes.

 

[350runner]

Cool! With the right gears it'll run like a bat out ah h!!! Sure the off-road gear heads will chime in.

 

[ruedger455]

Thats what im hoping for lol

 

[MadOgre]

4.56 sounds about right. might be a little on the low side for 37s though.

 

[ruedger455]

So if I put kn 4.56s and keep the 35s it should be good? 5.13s for 37s?

 

[MadOgre]

So if I put kn 4.56s and keep the 35s it should be good? 5.13s for 37s?

What tranny ?

Yes 4.56s will work for 35s.

Remember the higher you gear it the higher your rpms will be in top gear as well. So 5.13s would be better for low end torque but worse for highway cruising.

If its mainly an offroad vehicle and you think you might go with 37s then 5.13s are probably your best bet.

Its kinda expensive regearing so I would give it some thought and make sure that's what you want.

 

[ruedger455]

Its my daily driver. Sk I think im gonna go with 4.56s ill probably keep my 35s or just go to 36s at the most.

 

[ruedger455]

Its got a th350

 

[MadOgre]

Yep that should work good.

 

[ruedger455]

Awesome thanks guys

 

[marks86]

if this is your daily driver and you drive it on the highway, then you do not need 4.56 gears, specially with a three speed automatic, your truck is going to be screaming a 70mph

4.10 is a way better gear and alot more user friendly

ask me how I know this because I DD my truck with 4.56, my diesel which redlines at 3600 even with 37inch tall tires I redlined a 70, so driving around at 55 my truck would SCREAM anywhere I went and got terrible fuel mileage

 

[ruedger455]

I dont ever go on the highway the fastest I go is 55mph. I **** think ive ever had it at 70 lol. But so 4.10s would be a good idea to look into?

 

[marks86]

I dont ever go on the highway the fastest I go is 55mph. I **** think ive ever had it at 70 lol. But so 4.10s would be a good idea to look into?

what do you do with the truck more, have it in four wheel drive or rely on it to get you to work?